Queen Marcia was the mythical third queen regnant

Queen regnant

A queen regnant is a female monarch who reigns in her own right, in contrast to a queen consort, who is the wife of a reigning king. An empress regnant is a female monarch who reigns in her own right over an empire....

 and a regent

Regent

A regent, from the Latin regens "one who reigns", is a person selected to act as head of state because the ruler is a minor, not present, or debilitated. Currently there are only two ruling Regencies in the world, sovereign Liechtenstein and the Malaysian constitutive state of Terengganu...

 of the Britons, as recounted by Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

.

Mythical Account

Marcia became queen after the death of Guithelin

Guithelin

Guithelin was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He became king after the death of Gurguit Barbtruc.He ruled liberally and temperately for his life. His Queen consort was an artisan and noblewoman named Marcia. When he died, his wife took over the government...

 (Welsh

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

: Kyhylyn) and ruled as regent for her son, Sisillius II

Sisillius II

Sisillius II was a mythical king of the Britons as accounted by Geoffrey of Monmouth.-Mythical account:...

. In her youth, she was the Queen consort

Queen consort

A queen consort is the wife of a reigning king. A queen consort usually shares her husband's rank and holds the feminine equivalent of the king's monarchical titles. Historically, queens consort do not share the king regnant's political and military powers. Most queens in history were queens consort...

 of Guithelin, the king of Britain

British Iron Age

The British Iron Age is a conventional name used in the archaeology of Great Britain, referring to the prehistoric and protohistoric phases of the Iron-Age culture of the main island and the smaller islands, typically excluding prehistoric Ireland, and which had an independent Iron Age culture of...

. She was a noblewoman and knowledgeable in all the arts. Queen Marcia ruled Britain for about five years after Guithelin's death because their son was just seven years old at his father's death.

Queen Marcia was a learned woman who codified the Marcian Laws, the Lex Martiana. King Alfred the Great

Alfred the Great

Alfred the Great was King of Wessex from 871 to 899.Alfred is noted for his defence of the Anglo-Saxon kingdoms of southern England against the Vikings, becoming the only English monarch still to be accorded the epithet "the Great". Alfred was the first King of the West Saxons to style himself...

 was later to translate the code into Old English

English language

English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

as the basis of Mercian Laws, believing them to have been named after the much later Saxon kingdom of Mercia.

Sisillius (Welsh: Saessyllt), came to the throne in ca 358 BC on Queen Marcia's death.